What is the expected correct behavior?

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com

Possible fixes

Definitely think the breakpoints need to be specific to the navbar content and not rely on Bootstrap4's breakpoints.

Ideally, this shift of content needs to be conservative. Could potentially be dynamic, but using JS to calculate layout might not be performant enough for such an omnipresent component (almost all signed in pages).

Some additional info:

There are incoming issues that will affect the amount of content, so content amount is variable (if you're admin, etc.) so don't assume any fixed widths.